Q. If the wavelength of light is $4000\ \mathring{\mathrm{A}},$ then the number of waves in $1\ mm$ length will be
A) 25
B) 0.25
C) $0.25 \times 10^{4}$
D) $25 \times 10^{4}$
Explanation
(c) Number of waves $= \frac{10^{- 3}}{4000 \times 10^{- 10}} = 0.25 \times 10^{4}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.